In recent years, OA equipment digitalization has developed, and moreover, demand for color image output has increased. This has led to wide prevalence of an image forming apparatus such as an electrophotgraphic digital color copying machine, an electrophotgraphic complex machine, an ink jet color printer, or a thermal transfer color printer. For example, these image forming apparatuses are used for outputting image data or the like inputted into the image forming apparatuses from an image input device such as a scanner.
These image forming apparatuses need to output an image that properly reproduces a color of the image data inputted into the image forming apparatuses from the image input device or the like. Accordingly, color correction processing in which a digital image processing technique is used serves an important role in an image processing device for use in an image forming apparatus.
However, it is very troublesome work for an operator to set parameters for the color correction processing with respect to each original document. Moreover, in case, for example, the operator chooses an improper parameter, it is necessary to carry out another image formation after a parameter is newly set. This also means useless copy will be produced.
In an arrangement proposed for overcoming such a problem, a color correction processing is performed automatically.
For example, Patent Document 1 (Japanese Unexamined Patent Publication No. 153022/2003 (Tokukai 2003-153022) published on May 23, 2003) discloses a technique of (i) preparing in advance a look-up table storing color correction data and (ii), with reference to this look-up table, converting image data made of colors in a first color space into image data made of colors in a second color space.
Patent Document 2 (Japanese Unexamined Patent Publication No. 23771/2004 (Tokukai 2004-23771) published on Jan. 22, 2004) discloses a technique of (i) preparing a correction table on the basis of (a) a page-background color of an original document from which image data is read and (b) a page-background color of a recording sheet on which the image read from the original document is formed and (ii) performing a color correction processing according to the correction table thus prepared. Specifically, in Patent Document 2, the correction table is prepared so that a color correction processing is carried out in such a manner that (a) a color correction causing the page-background color of the original document to become visually recognized as an achromatic color is combined with (b) a color correction causing the page-background color of the recording sheet to become visually recognized as an achromatic color.
In contrast, the technique disclosed in Patent Document 1 performs a color correction processing with the use of a single look-up table no matter what color the page-background color of the original document is. Consequently, in a case where a page-background color removal is carried out, a color taste of a color which the user wishes it to stay unchanged changes largely. As a result, there arises a problem that a proper color reproduction becomes impossible. Especially, in a case of processing a light color image formed on a deep page-background color, a color reproducibility tends to deteriorate due to influence of the page-background color removal processing. Specifically, for example, a light pink image formed on a thick yellow page-background color may be reproduced as an orange image.
In Patent Document 2, since a color correction processing is carried out in such a manner that (a) a color correction causing the page-background color of the original document to become visually recognized as an achromatic color is combined with (b) a color correction causing the page-background color of the recording sheet to become visually recognized as an achromatic color, the technique of Patent Document 2, as well as the Patent Document 1, may reproduce a color improperly, depending on a combination of a page-background color of the original document and a page-background color of the recording sheet. Furthermore, the technique disclosed in Patent Document 2 requires, for each image formation, (i) operation of reading an image on the original document and the recording sheet and (ii) preparation of a correction table by identifying each page-background color of the original document and the recording sheet. This gives rise to problems such as an increase in complication of a device arrangement, an increase in size of the device, an increase in processing time, and an increase in power consumption.